Ask HN: Has anyone found a good co-founder using “founder dating” techniques?

There are many sites out there, such as FounderDating, FoundersHookUp, CoFoundersLab, etc., that attempt to help solo startup founders find a co-founder. (To clarify, I am a tech founder.)

Is there any evidence that this actually works to create a great founding team? Have you used it successfully?

Relatedly, might it be better to be a solo founder than to find a co-founder you don't already know well?